The disturbing electromagnetic field generates the difference mode current between line and line, which causes interference on the load. 

The disturbance electromagnetic field generates the common mode current on-line between the ground, and the common mode current generates 

the difference mode voltage on the load, causing interference, which is the common mode ground loop interference

The filter inductors that inhibit common mode interference are called common mode inductors. The filter inductance used to suppress differential 

mode interference is called differential mode inductance.

Common mode inductance is two sets of coils with equal winding number, equal wire diameter and opposite direction. Differential mode inductance 

is a coil wound around a core.

Common mode inductors are characterized by the fact that the two coils on the same core are wound in opposite directions, so the core is not 

afraid of saturation. The most widely used magnetic core material on the market is ferrite material.